Standard size staples have been used to staple stacks of paper, or other material, within predetermined ranges of stack thicknesses. In general, staples with longer legs are needed to staple thicker stacks than can be stapled with staples that have shorter legs. Standard staple sizes, for example, are configured for stapling ranges of stacks from 2 to 30 sheets or 30 to 70 sheets, for instance.
U.S. Pat. No. 4,318,555 teaches a stapler that cuts and forms staples from a continuous supply of wire. The height of the stack to be stapled is sensed, and the length of the wire to be cut is selected accordingly. The cut blank is then formed into a staple, which is then driven into the sheets to be stapled. As different wire lengths are selected, the staple is formed with legs of varying length, and a crown of a constant length.
U.S. Pat. Nos. 4,583,276 and 5,007,483 show staplers that employ the cartridge that includes a belt of straight, flat staple blank. The belt is fed to a former which bends the blanks to a single size. A driver then drives the formed staple towards an anvil with clinching grooves or clinching wings to bend the staple legs against the stack.
The invention is related to a stapler that can feed a staple blank of a predetermined length and form the blank into a staple selectably with a smaller or larger crown size, and preferably with corresponding larger or smaller leg length. Thus, a single source of staple blanks can be used to staple a large range of stack sizes, by varying the configuration of the staple produced.